Family researchers, policy makers, and the public generally perceive that declining marriage rates automatically and substantially increase the prevalence of non-marital fertility. The goal of the proposed research is to estimate the size of this relationship by modeling the pathways by which changes in marriage rates can influence non-marital fertility. The specific aims of the project are to examine how changes in childless U.S. women's rates of first marriage influence three factors: 1) changes in the duration of exposure to the risk of a first non-marital birth, 2) changes in the observed rate of first non-marital birth, due to changing population composition of the never-married population, and 3) changes in the observed rate of first non-marital birth, due to changes in the distribution or composition of the population of cohabiting, never-married women. In each aim, we use approaches that focus on how marriage rates influence exposure to risk of a non-marital first birth, and how this exposure influences the proportion of women who experience non-marital first births. The data for the study are from the National Survey of Family Growth (NSFG), and we focus on U.S. women at ages 20 to 29. Overall, our preliminary findings suggest that declines in marriage rates have influenced the proportion of U.S. women with a non-marital first birth through each of the three demographic processes listed above, but the magnitude of this influence could be smaller than predicted by many researchers (c.f. Gray, Stockard, and Stone 2006.)